1. The Field of the Invention
This invention relates broadly to measuring devices to measure conditions existing between a watercraft and the water surrounding the watercraft.
More particularly, it concerns new forms of (a) speedometers for small, high performance sailboats, sailboards, etc. and (b) depthmeters for boats that require no electricity to operate.
2. Description of the Prior Art
Inexpensive, reasonably reliable speedometers for boats are currently available, see U.S. pat. Nos. 2,733,601 and 4,122,711. Probably the majority of such speedometers utilize stagnation pressure for measurement of speed, i.e., they are Pitot tube devices, e.g., see U.S. Pat. Nos. 1,885,933 and 3,164,016.
Pitot tubes are peculiarly suited to measurement of speed through the water at speeds above five miles per hour. The pressure signal is normally read by inexpensive, diaphragm gages calibrated to read in miles per hour rather than pressure, see U.S. Pat. No. 3,349,615. The Pitot tube pickup is normally mounted to the transom of the boat with the pressure sensing hole slightly below the transom, facing in the forward direction, see U.S. Pat. No. 3,082,623.
There is a need for an inexpensive speedometer for high performance sailboats such as small racing catamarans and sailboards. A speedometer of this type must be unusually rugged because of the difficult environment, which includes frequent capsizings. Also the speedometer should be easy to install and remove so the it need not be left permanently on the craft. Because of the cramped and difficult conditions aboard sailboats of the stated type, the speedometer must be quite visible and easy to read. Devices of the present invention utilize stagnation pressure to provide new forms of watercraft speedometers that satisfy these special requirement of small, high performance sailcraft.
For the measurement of water depth from a boat, the most basic device for this purpose has historically been the lead line, i.e., a light line with a weight tied to one end to be thrown in the water and allowed to sink to the bottom of the water. As the line is retrieved, the length of line that was immersed in the water is determined, usually via tags or other markers spaced apart along the line.
Lead lines are too primitive for the desires of most boaters, so many forms of more sophisticated depthmeters have been developed most of which are based on the use of reflected sound waves for depth measurement. Such devices require electricity for operation, are relatively expensive and cannot withstand severe environments such as are encountered in small dinghies, open motorboats and sailboats or the like. Hence, there is a need for boating depthmeters that can report depth by a direct reading gage, but which are inexpensive, do not require electricity for operation and can survive harsh environments.